The effect of magnesium addition on the catalytic properties of PtSnK/gamma-Al2O3 catalyst for isobutane dehydrogenation has been investigated by reaction tests and some physicochemical characterizations such as nitrogen adsorption, TEM, H-2 chemisorption, TPR, H-2-TPD, and TPO. It was found that with the suitable addition of magnesium (0.2 and 0.4 wt.%), the platinum dispersion increased, while the carbon depositions decreased. The presence of Mg in the PtSnMgK/gamma-Al2O3 catalysts could not only strengthen the Sn-Al2O3 interaction, but also stabilize the oxidation states of Sn species, which resulted in the increased reaction activity and stability. However, when the content of magnesium was excessive (0.6 and 0.8 wt.%). the character of platinum and the interfacial properties between the metal and the support changed evidently, which was disadvantageous to the reaction. In our experiments, addition of 0.4 wt.% Mg to PtSnK/Al2O3 catalyst showed the best catalytic performance. After reaction for 6 h, selectivity toward isobutene of higher than 94% was achieved with the corresponding conversion value of about 29.0%. (C) 2011 Elsevier B.V. All rights reserved.